Re: Beta test of Postgresql 6.5

> 
> Hi again,
> 
> I'm trying to use your hint, but I don't find the new select sintax in the
> docs, so excuse me for asking again.
> If I've got it right, whe I make a SELECT ... FOR UPDATE within a connection
> (Autocommit = off), the selected records are blocked until the connection is
> closed, commited or rolled-back. Thus, only the same transaction can modify
> them, and consistency is thus achieved.
> 
> I've tried lauching two processes that make simultaneous updates on one
> table (different rows) and simultaneous inserts on another (these processes
> are client order imports from file). One of the processes run while the
> other kept waiting in the first insert it atempted. Do I have to use any SQL
> or configure something, or is this the normal behaviour?
> 
> Thanks again for your answers.

I assume you are running the snapshot, and not 6.4.*.  You are actually
using FOR UPDATE, so I think it is the snapshot.  

This is normal behavior, I think.  I believe the issue with SELECT FOR
UPDATE is that it has to lock the entire table.  We allow non-blocking
readers and non-blocking writers on different rows by using the
transaction id and multi-version system.  SELECT FOR UPDATE does not
actually modify any rows, so we can't look at any transaction id.

Vadim, can you comment?

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